2. Discussion of Prior Art
Fin systems using a box as an anchor require routing of the surfcraft before installing the box. For example, U.S. Pat. No. 4,379,703 (1983) to Mizell requires the use of a router to achieve high volume manufacturing of surfcraft. Until the early 1990's all removable fin systems required routing of the surfcraft for fin system anchor installation.
U.S. Pat. Nos. 5,328,397 (1994), 5,464,359 (1995), 5,672,081(1997) all to Whitty, and U.S. Pat. No. 6,764,364 (2004) to Hickman et al describe a system using two or more plugs per fin. These plugs require exact spacing from each other. If the spacing is not correct the fin will not fit into the plugs. This creates a problem requiring a special spacing tool and extra labor during manufacturing. These plugs have traditionally been installed using a jig during manufacturing. The jig is used to space the plugs correctly during manufacture of the surfcraft.
In the process of manufacturing a surfcraft, removable fin systems are usually installed after a coating of fiberglass and polyester resin is applied to a shaped polyurethane foam blank. Other materials can be used for a blank such as polystyrene foam, balsa wood, or some other light shapeable material. Other materials can be used for the coating such as epoxy resin.
The removable fin system anchor is usually installed after the fiberglass coating is applied and cured. These anchors are most commonly installed before the fiberglass coating is sanded. Several fin systems use a box or plug as an anchor. The anchors are adhered into the surfcraft using a material compatible with the surfboard coating and blank. Polyester resin is one such adhesive material. These anchors sometimes include a raised skirt. This raised skirt prevents resin from flowing into the fin system anchor recess. The recess is made to accept a feature from the fin. The recess must be free of excess material. The recess is below the surface of the surfboard. Excess resin can easily flow into this recess during surfboard manufacture. The resin cures around the anchor adhering it to the surfcraft. After the resin cures the entire surfcraft is sanded. The resin connects the anchor to the surfcraft. The skirts are simply sanded away leaving a smooth surface above the fin system anchor. The skirt prevents resin from going into the recess, curing, and making the anchor unusable.
U.S. Pat. No. 5,975,974 (1999) to McCausland joins three plugs together. This allows spacing between the front and back recesses to be very accurate. This advantage is not realized because of the added weight. Also, the large perimeter, or edge between the anchor and resin coating, is prone to water leaks. One of the main advantages of plugs, the small perimeter, is eliminated in this design. Also, as the tail portion of the surfcraft flexes, this stiff box-like design changes the performance of the surfcraft.